Your data may not be saved in Google Sheets if:
You do not have permission on changing the file
The sheet has merged or protected cells
The sheet is out of space
The name of the tab in the google sheet has been changed, so the plugin cannot find a place to save the data. In this case, you need to connect the Google spreadsheet again.
The data is usually stored in the first free line. If a line has any formulas, it is considered occupied. Please check all of these points for your google spreadsheet.